Basic operation of standard internal combustion (IC) engines varies based on the type of combustion process, the quantity of cylinders and the desired use/functionality. For instance, in a traditional two-stroke engine, oil is pre-mixed with fuel and air before entry into the crankcase where the oil/fuel/air mixture is ignited. In a gasoline engine, fuel is pre-mixed with only air, but is then compressed and ignited by a spark plug that causes the fuel to burn. In a diesel engine, fuel and air are pre-mixed but as there is no spark plug to provide ignition, the fuel/air mixture is ignited by compression in the piston shaft. In each type of IC engine, following fuel ignition, the piston is then pushed downwardly and the exhaust fumes are allowed to exit the cylinder when the piston exposes the exhaust port. The movement of the piston pressurizes the remaining oil/fuel in the crankcase and allows additional fresh oil/fuel/air to rush into the cylinder, thereby simultaneously pushing the remaining exhaust out the exhaust port.
Momentum drives the piston back into the compression stroke as the process repeats itself.
In a diesel or gasoline powered engine, as opposed to a two-stroke engine, oil lubrication of the crankshaft and connecting rod bearings is separate from the fuel/air mixture. In a diesel or gasoline powered engine, the crankcase is filled mainly with air and oil. It is the intake manifold that receives and mixes fuel and air from separate sources. The fuel/air mixture in the intake manifold is drawn into the combustion chamber where it is ignited by the spark plugs (in a gasoline engine) and burned. There are no spark plugs in a diesel engine, so ignition in a diesel engine occurs as a result of compression in the piston shaft. The combustion chamber, in both gasoline and diesel engines, is largely sealed off from the crankcase by a set of piston rings that are disposed around an outer diameter of the pistons within the piston cylinder. This keeps the oil in the crankcase rather than allowing it to burn as part of the combustion stroke. Unfortunately, the piston rings are unable to completely seal off the piston cylinder. Consequently, small amounts of crankcase oil intended to lubricate the cylinder are instead drawn into the combustion chamber and burned during the combustion process. This is true in both gasoline and diesel powered engines. Additionally, combustion waste gasses comprising unburned fuel and exhaust gases in the combustion chamber simultaneously pass the piston rings and enter the crankcase. The waste gas entering the crankcase is commonly called “blow-by” or “blow-by gas”.
Blow-by gases mainly consist of contaminants such as hydrocarbons (unburned fuel), carbon dioxide or water vapor, all of which are harmful to the engine crankcase. The quantity of blow-by gas in the crankcase can be several times that of the concentration of hydrocarbons in the intake manifold. Simply venting these gases to the atmosphere increases air pollution. Alternatively, trapping the blow-by gases in the crankcase allows the contaminants to condense and accumulate over time in the engine crankcase. Condensed contaminants form corrosive acids and sludge in the interior of the crankcase. This decreases the ability of the engine oil in the crankcase to lubricate the cylinder and crankshaft. Degraded oil that fails to properly lubricate the crankshaft components (e.g. the crankshaft and connecting rods) can be a factor in increased wear and tear in the engine, as well as poor engine performance. Inadequate crankcase lubrication contributes to unnecessary wear on the piston rings which simultaneously reduces the quality of the seal between the combustion chamber and the crankcase. As the engine ages, the gaps between the piston rings and cylinder walls increase resulting in larger quantities of blow-by gases entering the crankcase. Too much blow-by gases entering the crankcase can cause power loss and even engine failure. Moreover, condensed water in the blow-by gases can cause engine parts to rust. Hence, crankcase ventilation systems were developed to remedy the existence of blow-by gases in the crankcase. In general, crankcase ventilation systems expel blow-by gases out of a positive crankcase ventilation (PCV) valve and into the intake manifold to be re-burned.
The PCV valve recirculates (i.e. vents) blow-by gases from the crankcase back into the intake manifold to be burned again with a fresh supply of air/fuel during combustion. This is particularly desirable as the harmful blow-by gases are not simply vented to the atmosphere. A crankcase ventilation system should also be designed to limit, or ideally eliminate, blow-by gas in the crankcase to keep the crankcase as clean as possible. Early PCV valves comprised simple one-way check valves. These PCV valves relied solely on pressure differentials between the crankcase and intake manifold to function correctly. When a piston travels downward during intake, the air pressure in the intake manifold becomes lower than the surrounding ambient atmosphere. This result is commonly called “engine vacuum”. The vacuum draws air toward the intake manifold. Accordingly, air is capable of being drawn from the crankcase and into the intake manifold through a PCV valve that provides a conduit in-between the crankcase and intake manifold. The PCV valve basically opens a one-way path for blow-by gases to vent from the crankcase back into the intake manifold. In the even the pressure difference changes (i.e. the pressure in the intake manifold becomes relatively higher than the pressure in the crankcase), the PCV valve closes and prevents gases from exiting the intake manifold and entering the crankcase. Hence, the PCV valve is a “positive” crankcase ventilation system, wherein gases are only allowed to flow in one direction—out from the crankcase and into the intake manifold. The one-way check valve is basically an all-or-nothing valve. That is, the valve is completely open during periods when the pressure in the intake manifold is relatively less than the pressure in the crankcase. Alternatively, the valve is completely closed when the pressure in the crankcase is relatively lower than the pressure in the intake manifold. One-way check valve-based PCV valves are unable to account for changes in the quantity of blow-by gases that exist in the crankcase at any given time. The quantity of blow-by gases in the crankcase varies under different driving conditions and by engine make and model.
PCV valve designs have been improved over the basic one-way check valve and can better regulate the quantity of blow-by gases vented from the crankcase to the intake manifold. One PCV valve design uses a spring to position an internal restrictor, such as a cone or disk, relative to a vent through which the blow-by gases flow from the crankcase to the intake manifold. The internal restrictor is positioned proximate to the vent at the distance proportionate to the level of engine vacuum relative to spring tension. The purpose of the spring is to respond to vacuum pressure variation between the crankcase and intake manifold. This design is intended to improve on the all-or-nothing one-way check valve. For example, at idle, engine vacuum is high. The spring-biased restrictor is set to vent a large quantity of blow-by gases in view of the large pressure differential, even though the engine is producing a relatively small quantity of blow-by gases. The spring positions the internal restrictor to substantially allow air flow from the crankcase to the intake manifold. During acceleration, the engine vacuum decreases due to an increase in engine load. Consequently, the spring is able to push the internal restrictor back down to reduce the air flow from the crankcase to the intake manifold, even though the engine is producing more blow-by gases. Vacuum pressure then increases as the acceleration decreases (i.e. engine load decreases) as the vehicle moves toward a constant cruising speed. Again, the spring draws the internal restrictor back away from the vent to a position that substantially allows air flow from the crankcase to the intake manifold, based on the pressure differential, because the engine creates more blow-by gases at cruising speeds due to higher engine RPMs. Hence, such an improved PCV valve that solely relies on engine vacuum and a spring-biased restrictor does not optimize the ventilation of blow-by gases from the crankcase to the intake manifold, especially in situations where the vehicle is constantly changing speeds (e.g. city driving or stop and go highway traffic).
One key aspect of crankcase ventilation is that engine vacuum varies as a function of engine load, rather than engine speed, and the quantity of blow-by gases varies, in part, as a function of engine speed, rather than engine load. For example, engine vacuum is higher when engine speeds remain relatively constant (e.g. idling or driving at a constant velocity). Thus, the amount of engine vacuum present when an engine is idling (at say 90° rotations per minute (rpm)) is essentially the same as the amount of vacuum present when the engine is cruising at a constant speed on a highway (for example between 2,500 to 2,800 rpm). The rate at which blow-by gases are produced is much higher at 2,500 rpm than at 900 rpm. But, a spring-based PCV valve is unable to account for the difference in blow-by gas production between 2,500 rpm and 900 rpm because the spring-based PCV valve experiences a similar pressure differential between the intake manifold and the crankcase at these different engine speeds. The spring is only responsive to changes in air pressure, which is a function of engine load rather than engine speed. Engine load typically increases when accelerating or when climbing a hill, for example. As the vehicle accelerates blow-by gas production increases, but the engine vacuum decreases due to the increased engine load. Thus, the spring based PCV valve may vent an inadequate quantity of blow-by gases from the crankcase during acceleration. Such a spring-based PCV valve system is incapable of venting blow-by gases based on blow-by gas production because the spring only responds to engine vacuum.
Maintenance of a PCV valve system is important and relatively simple. The lubricating oil must be changed periodically to remove the harmful contaminants trapped therein over time. Failure to change the lubricating oil at adequate intervals (typically every 3,000 to 6,000 miles) can lead to a PCV valve system contaminated with sludge. A plugged PCV valve system will eventually damage the engine. The PCV valve system should remain clear for the life of the engine assuming the lubricating oil is changed at an adequate frequency.
As part of an effort to combat smog in the Los Angeles basin, California started requiring emission control systems on all model cars starting in the 1960s. The Federal Government extended these emission control regulations nationwide in 1968. Congress passed the Clear Air Act in 1970 and established the Environmental Protection Agency (EPA). Since then, vehicle manufacturers have had to meet a series of graduated emission control standards for the production and maintenance of vehicles. This involved implementing devices to control engine functions and diagnose engine problems. More specifically, automobile manufacturers started integrating electrically controlled components, such as electric fuel feeds and ignition systems. Sensors were also added to measure engine efficiency, system performance and pollution. These sensors were capable of being accessed for early diagnostic assistance.
On-Board Diagnostics (OBD) refers to early vehicle self-diagnostic systems and reporting capabilities. OBD systems provide current state information for various vehicle subsystems. The quantity of diagnostic information available via OBD has varied widely since the introduction of on-board computers to automobiles in the early 1980s. OBD originally illuminated a malfunction indicator light (MIL) for a detected problem, but did not provide information regarding the nature of the problem. Modern OBD implementations use a standardized fast digital communications port to provide real-time data in combination with standardized series of diagnostic trouble codes (DTCs) to establish rapid identification of malfunctions and the corresponding remedy from within the vehicle.
The California Air Resources Board (CARB or simply ARB) developed regulations to enforce the application of the first incarnation of OBD (known now as “OBD-I”). The aim of CARB was to encourage automobile manufacturers to design reliable emission control systems. CARB envisioned lowering vehicle emissions in California by denying registration of vehicles that did not pass the CARB vehicle emission standards. Unfortunately, OBD-I did not succeed at the time as the infrastructure for testing and reporting emissions-specific diagnostic information was not standardized or widely accepted. Technical difficulties in obtaining standardized and reliable emission information from all vehicles led to an inability to effectively implement an annual testing program.
OBD became more sophisticated after the initial implementation of OBD-I. OBD-II was a new standard introduced in the mid 1990s that implemented a new set of standards and practices developed by the Society of Automotive Engineers (SAE). These standards were eventually adopted by the EPA and CARB. OBD-II incorporates enhanced features that provide better engine monitoring technologies. OBD-II also monitors chassis parts, body and accessory devices, and includes an automobile diagnostic control network. OBD-II improved upon OBD-I in both capability and standardization. OBD-II specifies the type of diagnostic connector, pin configuration, electrical signaling protocols, messaging format and provides an extensible list of diagnostic trouble codes (DTCs). OBD-II also monitors a specific list of vehicle parameters and encodes performance data for each of those parameters. Thus, a single device can query the on-board computer(s) in any vehicle. This simplification of reporting diagnostic data led to the feasibility of the comprehensive emissions testing program envisioned by CARB.
A problem exists in that all the diagnostic information coming from the OBD-II system is not being used in order to optimize the performance of the engine; specifically with regard to the PCV valve. Accordingly, there is a need for a microcontroller apparatus and system that utilizes engine diagnostic information in order to optimize performance of the PCV valve thereby reducing engine emissions and pollution. The present invention fulfills these needs and provides other related advantages.